Condenser and process



10, 1931. w p ss 1,795,504

CONDENSER AND PROGES S Original Filed April 30, 1920 INVENTOR )7744/0? J6 7375 S5 ATTORNEY Patented Mar. 10, 1931;

UNITED STATES PATENT OFFICE WILIILAM H. PRIESS, OF UPPER MONTCLAIR, NEW JERSEY, ASSIGNOR T0 WIRELESS SPECIALTY APPARATUS COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF. NEW YORK CONDENSER AND PROCESS Original application filed April 30, 1920, Serial No. 377,977. Divided and this application filed November 16, 1927. Serial No. 233,574.

One of the first steps in the process of making condensers consists in assembling alternate sheets of conducting and dielectric materials to build upa condenser stack of the required height, these sheets of material being separated by insulation having suitable properties for this peculiar class of work. Notwithstanding great care in selecting these materials and in assembling them, it is a very common experience to have a condenser break down during test or while in use and it has been definitely determined that a very important cause of such breakdowns is the presence of voids, gas, or an excessive amount of insulating material between the sheets of material that make up the condenser.

It is an important object of the present invention to devise a process of making condensers which will reduce to a minimum imperfections and faults of the character above mentioned. In other words the invention aims to devise a process of building condensers which will eliminate an unnecessary thickness of insulating material between the layersof conducting and dielectric materials that make up the condenser and which will also reduce to a minimum the presence. of voids, blisters or bubbles in the condenser. It is also an object of the invention to devise a process of making condensers which will produce a condenser that is a firm mechanical mass, that will have a very low dielectric loss and in which the leakage between successive conducting elements of the condenser will be reduced to a minimum. A further object of the invention is to improve condenser con-,

structions both from an electrical and also from a mechanical standpoint.

This application is a division of my copending application Serial No. 377,977, filed April 30, 1920.

The invention also consists in certain new and original features of construction and combinations of parts hereinafter set forth and claimed;

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claim ap ended hereto, the invention itself as to its obyects and advantages, the mode of its operation and the manner of its organization may be better understood by referring to the following description taken in connection with the accompanying drawings forming a part thereof, in which- Fig. 1 is a perspective view of a finished condenser;

Figs. 2 and 8 are plan and side views respectively of a baking clamp; and

Fig. 4 is a View similar to Fig. 3 but shows a condenser secured in the clamp.

Like reference characters denote like parts in the several figures of the drawings.

In the following description and in the claim parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit.

Assuming that the mica or other dielectric elements to be used in the condenser have been made by splitting the mica sheets to the desired thickness and cutting them out to the required shape and dimensions, and also that the tinfoil or other conducting elements of suitableshape and size have been provided, the next step is to coat the mica elements with varnish or other adhesive insulating material. It-is desirable that this coating shall be very thin and that it shall completely cover both surfaces of each mica sheet. This coat ing operation may be performed in any suitable manner and with any suitable insulating material such, for example, as varnish.

After the dielectric elements have been coated and partially dried, they are next assembled with sheets of tin foil, or other conducting material of the proper size and shape, to form a condenser stack. Aligned holes 25 in the dielectric elements and foil sheets may extend through the entire stack and provide i means for readily aligning the various'elements as by the insertion of suitable pins therein. The stack is preferably formed with foils of opposite potential extending from opposite sides thereof in line with the holes 25..

The condenser stack may either be built up in the form of a tall stack that later is split up into units of the required height, or the stack may be built up in the form of individi when a condenser is in use there is a tendency for the current to discharge from the edge of one of the conducting elements across the inactive margin to the edge of the next adjacent conducting element. Ordinarily a comparatively free path is left for this dis charge over the surface of the mica. The sealing of these marginal spaces, however,

by varnish introduces a solid wall-of insu-' lating material in the path of this discharge and thus reduces very substantially the sur face leakage that otherwise would be present in the condenser. In other Words, this construction reduces the electrical loss in the condenser. I

After the baking operation has been completed, the condenser. will be found to be a firm, mechanical mass capable of withstanding very rough usage. The sealing of the edges, as above described, contributes to this i which I prefer at present, the condenser units This second baking need not result and also is of advantage when the condenser is to be used in a damp location.

After the condenser has been baked its manufacture may be completed in any desired manner. According, to the process are next tested and any units which fail to withstand the tests are discarded. The units whichsuccessfu'lly come through the testing operation, however, next have the projecting ends of foil trimmed ofi and suitable clips, such for instance as those indicated at 30 and 31 in Fig. 1 are secured to the opposite edges of the condenser in contact with the respective sets of foil elements. In order to reduce still further the electrical losses in the con denser and also for the purpose of improving its mechanical structure, it is preferable under some conditions to repeat the baking operation. Before this baking is begun, however, I prefer to coat the edges of the condenser sheets with varnish in order to seal any cracks in it or to check any tendency to split that may have been started by the clipping operation of attaching clip; 30 and 31.

as long as the first but usually is from six to eight hours at a temperature from 110 degrees to 115 degrees C. The exact nature of the change produced in the condenser by this second baking is diflioult to determine but probably is due to some change produced in the exceedingly thin film of. varnish that continued still remains between the adjacent elements of the condenser. I have determined, however, by actual test that the electrical characing. The degree of improvement, however,

decreases with successive bakings and usually it is not advisable from a manufacturing standpoint to carry the-condenser through more than two of these heat cycles.

For the purpose of compressing the condenser stack durin the baking of the condenser after the clips have been secured to the condenser, I prefer to use a novel form of baking clamp illustrated in Figs. 2, 3 and 4. This clamp comprises a base 33 having a threaded post or pin 34 secured thereto at one end. Another screw threaded post35 is secured to the opposite end of the base by a pivot 36. A spring plate 37 has a hole through one end to fit loosely on the pin 34: and is notched at its opposite end to receive the swinging pin 35, the upward movement of this spring on the post 34 being limited by a nut 38 threaded on this post and adjustably secured in position by a set screw 39. The condenser is clamped between this spring plate 37 and the base 33 by pressure exerted on the spring through a nut 40 threaded on the pin 35. Inorder to enable this apparatus to exert pressure uniformly over the entire surface of the condenser, a plate 41 is removably secured to the upper surface of the base 33 by means of a screw 42, this plate being shaped to fit the lower face of the condenser between the clips. A similar plate 43 is secured to the lower face of the spring 37, this plate being provided with a locating pin 44 and a threaded stud 45that project through the spring plate and being held in position by a nut 46 threaded on the stud 45. This plate fits the upper surface of the condenser between the clips.

The apparatus is very convenient for use inbaking condensers after the clips have been applied to them whether such baking is for v the purpose of improving the electrical characteristics of the condenser or is for the purpose of baking on a label or cover slip, or for any other reason. It will be seen that after the nut 38 has been adjusted at the proper height to take a condenser of a given thickness, it is unnecessary to change the adj ustment of this nut again until another size of condenser is to be baked. The condenser is slipped betweeen the plates 41 and 43, the p1n-35 is swung into. its upright position, as shown in Fig. 12, and the nut 40 is quickly turned down to straighten the spring plate 37, as shown in Fig. 13, thus applying a fair- 1y heavy pressure to the condenser. After the baking operation has been completed the condenser can be quickly removed by reversing the operations above described. A further advantage of this construction is that the plates 41 and 43 can be quickly changed v to accommodate different sizes and styles of condensers.

5 lVhile the foregoing description has referred to the coating of the dielectric e1e- -1nents of the condenser, it would be possible to coat the conducting elements instead or to coat both sets of elements with an insulating material more or less. In some cases, however, it is not practicable to coat the conducting elements because they are too thin and flimsy and it is necessary to coat one set only of these elements. It is not regarded, therefore, as a departure from this invention to coat the other elements of the condenser if desired, nor is it regarded as a departure to use an adhesive material other than varnish, this material being mentioned specifically because it is preferred for the particular type of condenser specifically described herein.

\Vhile certain, novel features of the invention have been shown and described and are pointed out in the annexed claim, it will be understood that variousomissions, substitutions and changes in the forms and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

\Vhat is claimed is:

A sheet condenser Which consists of a stack of interleaved sheets of mica and metal foils, all formed With pairs of registering holes extending through the stack; the foils of opposite potential projecting in line with said holes from spaced-apart portions of the side of the stack, and a pair of terminal clips secured to the stack at locations for their con- 40 tact respectively with said projecting foils of opposite potential, said clips terminating short of said registering holes.

In testimony whereof I hereunto aflix my signature.

XVILLIAM H. PRIESS. 

